#13581: UNPACK should allow recursion that obviously terminates -------------------------------------+------------------------------------- Reporter: ryanreich | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I want to do this: {{{ {-# LANGUAGE TypeFamilies MagicHash KindSignatures #-} data Peano = Zero | Succ Peano data family BigWord (n :: Peano) data instance BigWord Zero = MachineWord# Word# data instance BigWord (Succ n) = BigWord {-# UNPACK #-}(BigWord n) {-# UNPACK #-}(BigWord n) }}} However, the compiler tells me that it is ignoring the UNPACKs, and the only reason I can see is that they are apparently recursive. This exact type of recursion is handled just fine in instance declarations because the recursive instance has fewer type constructors than the head; can't UNPACK do the same thing? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13581 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler